Thickly remove the peel from the oranges and cut into slices. Stir the honey and liqueur together. Place the orange slices in an ovenproof dish and drizzle with the honey-liqueur mixture.
Finely grind the pistachios. Whip egg whites and powdered sugar until very stiff. Fold in pistachios and cinnamon.
Put the meringue mixture into a piping bag with a nozzle and decorate the orange slices with it.
Place under a heated grill and gratinate for about 7 minutes. Garnish with mint leaves.
Preparation time: 35 min